1. Technical Field
The present invention relates to a plasma processing method and apparatus for performing plasma processing by using a plasma on, for example, objects (objects to be processed) such as a substrate having a thin film formed on its surface or processing objects coated with various types of films so that desired fine linear portions are worked with high precision, or for performing plasma processing by using a plasma on the surface of various processing objects so that a thin film is deposited thereon.
2. Description of Related Art
In general, when an object to be processed typified by a substrate with a thin film formed thereon is subjected to a patterning process, a resist process is used. FIGS. 7A to 7D show one example of the process. In FIGS. 7A to 7D, first, photosensitive resist 14 is applied onto the surface of an object 12 to be processed (FIG. 7A). Next, the resist 14 is exposed to light with an exposer and thereafter developed, by which the resist 14 can be patterned into a desired configuration (FIG. 7B). Further, with the object 12 placed in a vacuum chamber, a plasma is generated in the vacuum chamber and the processing object 12 is etched with the resist 14 used as a mask, by which the surface of the processing object 12 is patterned into a desired configuration (FIG. 7C). Finally, the resist 14 is removed with an oxygen plasma, organic solvent, or the like, and thereby the processing is completed (FIG. 7D).
The above-described resist process, which is suitable for forming a fine pattern with high precision, has come to play an important role in manufacturing semiconductors or other electronic devices. However, the known process is complicated.
Accordingly, new plasma processing methods without the use of any resist process have been under discussion. As an example thereof, a plasma source that linearly generates a plasma will be described with reference to FIGS. 8 and 9. FIG. 8 shows a perspective view of a plasma processing apparatus that has a plasma source with a plate-shaped electrode 1 mounted thereon, and FIG. 9 shows a sectional view taken along the plane PP of FIG. 8. In FIGS. 8 and 9, plate-shaped insulators 2, 3 are disposed at positions where the plate-shaped electrode 1 and their plate surfaces become mutually parallel, and gas can be supplied generally perpendicularly to the object 12 from a gas supply unit 10 via a gas passage 6. By applying a high-frequency power of 13.56 MHz to the plate-shaped electrode 1 from a high-frequency power supply 13 while supplying the gas from the gas supply unit 10, a plasma is generated between the plasma source including the plate-shaped electrode 1 and the object 12, so that the processing object 12 can be processed with the plasma. A distance “a” between the plasma source and the processing object 12 is 0.3 mm, thicknesses “b” and “c” of the plate-shaped electrode 1 and the plate-shaped insulators 2, 3 are both 1 mm, a width “e” of the gas passage 6 is 0.1 mm, and an angle of a pointing edge portion “i” of the plate-shaped electrode 1 is 60°. Also, the plate surface of the plate-shaped electrode 1 has a height “g” of 50 mm and a length “h” of 30 mm in the line direction.
For example, under the conditions that He is supplied by 1000 sccm and SF6 is supplied by 10 sccm as gas to the gas passage 6 and a high-frequency power of 100 W is supplied, as the object 12 of Si to be processed can be etched.
However, the etching by the plasma processing method and apparatus described in connection with the prior art example has had an issue in that the object would be processed over a wide range beyond desired fine linear portions. A resultant etching profile is shown in FIG. 10. In this case, given a depth D of the portion that is most deeply etched, if the width of a portion shallower than the pattern bottom by D×0.8 is a processing width E, then E was 2.1 mm. Since the thickness of the plate-shaped electrode 1 of the plasma source is 1 mm, the resulting processing width E was about double.